1. Field of the Invention
The present invention relates to a liquid crystal display device in which film thickness irregularities and rubbing irregularities of orientation films are minimized in which superior image quality is provided even when columnar spacers are disposed therein.
2. Description of the Related Art
A liquid crystal display device generally has a structure in which a liquid crystal substance is sandwiched between a pair of substrates facing each other. Image display by the liquid crystal display device is achieved by applying a voltage between the pair of substrates, and by controlling the light transmissivity based on the double refraction phenomenon displayed by liquid crystal substances. Thus, if the space between the substrates facing each other is not uniform in a screen, the intensity of the electric field applied between electrodes facing each other becomes different in the screen, and deterioration of the image quality occurs. Thus, in conventional practice, the space between a pair of substrates is controlled by scattering a given amount of small glass beads on one substrate as space keeping members, and as a result, due to the dispersion of the glass beads in the liquid crystal substance, the spacing of the pair of substrates is controlled.
It is however very difficult to uniformly scatter glass beads on the substrate, and sometimes, the glass beads are unevenly distributed (localized) on the screen, resulting in degradation of the image quality.
In recent years, instead of scattering glass beads on the substrates, space keeping members, an insulating resin such as a photosensitive resin or an insulator such as an oxide film consisting of SiO2 or the like formed in islands (i.e., columnar spacers independent from each other), is provided on one of a pair of substrates facing each other using photo-lithographic technology and etching technology to achieve superior positional accuracy, dimensional accuracy and shape accuracy.
However, an orientation film consisting of polyimide (PI) or the like is formed and rubbed after columnar spacers are formed, and if the columnar spacers are formed unevenly, noticeable film thickness irregularities or rubbing irregularities attributable to the unevenness of the columnar spacers themselves can be generated when forming the orientation film, and thus, the liquid crystal orientation becomes abnormal, resulting in a degradation of the image quality of the liquid crystal display device.
Accordingly, it is an object of the present invention to solve problems in the conventional technology, and in particular, to provide a liquid crystal display device in which film thickness irregularities and rubbing irregularities of an orientation film are minimized and in which superior image quality is provided even when columnar spacers are disposed therein.
The inventors of the present invention have found that the above-described problem can be solved or mitigated by limiting the placement density, the array, the size, etc. of columnar spacers in a given range, and have thus realized the present invention.
There is provided a liquid crystal display device having a structure in which a liquid crystal substance is sandwiched between a pair of substrates facing each other with the space therebetween controlled to a specific value by a plurality of columnar spacers independent from each other, wherein the placement density of the columnar spacers is 100 to 2000/mm2.
There is provided a manufacturing method of the liquid crystal display device having a structure in which a liquid crystal substance is sandwiched between a pair of substrates facing each other including a step in which columnar spacers are disposed on one of a pair of the substrates disposed at a placement density of 100 to 2000/mm2.